Beam Defocuses When Using the PfE Image Aquire

[John Donovan]

I'm not in favor of sending beam control commands after the user has carefully set the image focus, only to see that overridden by values that might be stale.

Hi Paul,
Good to know the 8200 doesn't have this issue. 

I agree with your statement that we should not be sending commands that change the focus prior to image acquisition. But currently, in PFE, the Digitize Image and Imaging windows *do* send a beam size zero command just prior to the image acquisition in PFE.  This is because if one is using a default beam size of 5 or 10 um, then the image will be acquired out of focus if the beam size zero command is not sent.

So you, I and Bill Mushock (and just spoke with Dave Adams) all agree that we should change this behavior so that we *do not* send a beam size zero command just prior to image acquisition. That is the default state of the beam size should always be zero, unless a sample acquisition is being performed.

So we propose the following:

1. When a sample acquisition is finished, reset the beam size back to zero, even the if the default beam size is not zero.

2. Prior to the image acquisition, do not set the beam size to zero.  That is, always assume that the current beam conditions are correct just prior to image acquisition.

3. However, for image acquisition *during automation*, we will have to set the beam size to zero prior to image acquisition, since the beam will already be at the default beam size which might be non zero.

How does this sound to everyone?

[Paul Carpenter]

That sounds like the best plan to me.

[John Donovan]

That sounds like the best plan to me.

There's always a complication!

Something I just thought of: what if the user just set the beam size to non-zero from the Analytical Conditions dialog?  We'd want it to be reset to zero when acquiring an image.  Or if they re-set the beam size to non-zero from another application, such as the JEOL software?

I have to think more about this...

Edit by John: OK, the beam size does automatically get reset to zero after an acquisition *if* the Default Focus checkbox is checked in the Analytical Conditions dialog!

I think I know what to do now.  Thanks for everyone's help on this!

[John Donovan]

OK, we've made a small change in the imaging code that we think should avoid the issue that Bill Mushock is reporting on his JEOL 8900.

But it should first be pointed out that the "Default Focus" feature, seen here:



is key to this situation.  Basically, when this box is checked (in the Analytical Conditions dialog in PFE), whenever an acquisition or automation completes, the software re-sets the beam size to zero.  The idea being that one can then simply unblank the beam and image with a fully focused beam. This is the default mode in PFE as many of you already know, but it essentially has no effect if the default beam size is already zero (fully focused).

However, if the user prefers to leave the beam size non-zero (for whatever reason), simply uncheck this box and the beam will always stay at the specified (non-zero) beam size.

Now, when it comes to image acquisition, the latest v. 12.7.8 PFE will first check if the beam size is already zero, and if it is already zero, it will not change the beam size. We think this will take care of the OL changes that Bill is seeing on his JEOL 8900 when the beam size is reset to zero.

But if for some reason the beam size is left at a non-zero value, or reset by other software to be non-zero, the imaging code will reset the beam size to zero, ensuring that the image acquired is fully focused.

Please let us know how this works for you all.

Edit by John:  In summary, I suggest everyone use the Default Focus feature so the beam is generally at beam size zero. Then when one starts an image acquisition, the beam is already at size zero, so the beam size command is not sent.